Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.40	5.265%	$69.896	$69.90	$69.90	$69.90
Purchase #2	$201.43	9.722%	$221.013	$221.01	$221.00	$221.00
Purchase #3	$43.80	6.750%	$46.7565	$46.76	$46.75	$46.80
Purchase #4	$103.50	7.731%	$111.5016	$111.50	$111.50	$111.50
Purchase #5	$88.45	9.354%	$96.7236	$96.72	$96.70	$96.70
Purchase #6	$27.92	4.515%	$29.1806	$29.18	$29.20	$29.20
Purchase #7	$114.87	7.593%	$123.5921	$123.59	$123.60	$123.60
7 purchase totals =	$646.37		$698.6634	$698.66	$698.65	$698.70